P2179: System Too Lean Off Idle (Bank 2)

P2179 is the bank 2 version of P2177 on engines with a front oxygen sensor for each cylinder bank: the load-dependent, multiplicative share of bank 2's long-term correction has reached its lean limit. GM's 2005 2.8 and 3.6 V6 and the 2008 3.6 LLT use a factor above 1.23, GM's 2024 tables above 1.27, both over two trips. VW's 2014 Touareg sets it for the 3.0 TSI hybrid and the 3.6 VR6 when bank 2 adaptation exceeds +30 %. If both banks are lean at load, look at what they share: fuel pressure, the pump, the air mass sensor. If bank 2 alone is affected, the cause lies on that side, such as a restricted injector, an intake leak at that bank's manifold or a front sensor reading lean. No bulletin naming this code was found.

Bank 2 is the side without cylinder 1, so it only exists on V or boxer engines.

Symptoms

• Check engine lamp on after two trips
• Hesitation under load

Most likely causes

• Low fuel pressure or air mass sensor fault, usually with P2177 too
• Restricted injector on bank 2
• Intake leak or front oxygen sensor fault on bank 2

What to check, in order

Start with the simplest. You can tick off each step.

1. Check short-term and long-term fuel trims in live data
2. Look for air leaks at hoses and gaskets
3. Check the mass air flow sensor (MAF) and, if appropriate, clean it with a dedicated cleaner
4. Measure the fuel pressure
5. Check the injectors and the oxygen sensor

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P2179 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 1: Air and fuel
• 79: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2179?

You can drive in moderation for a short time. A very lean or very rich mixture can damage the engine or the catalytic converter.

What causes code P2179?

The most common causes are: low fuel pressure or air mass sensor fault, usually with P2177 too; restricted injector on bank 2; intake leak or front oxygen sensor fault on bank 2.

Related codes

• P2177System Too Lean Off Idle (Bank 1)
• P2180System Too Rich Off Idle (Bank 2)
• P2189System Too Lean at Idle (Bank 2)
• P0174System Too Lean Bank 2

Sources

• gsi.ext.gm.com: 2005file14
• gsi.ext.gm.com: 08 GRP02 LLT Engine
• gsi.ext.gm.com: 24OBDG07
• static.nhtsa.gov: MC 10074008 2280

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.